VMWare questions

[bogstad-e+AXbWqSrlAAvxtiuMwx3w at public.gmane.org (Bill Bogstad)]

On Fri, Dec 3, 2010 at 2:29 PM, Jerry Feldman <gaf-mNDKBlG2WHs at public.gmane.org> wrote:
> Since we are on the subject of virtualization, I have a few questions.
> First, we have 5 Supermicro based servers each with 64GB of memory and
> Intel Woodcrest 2 dual core 2.66 GHz CPUs + 1 6U monster with 4
> Woodcrest 3.4GHz CPUs. We are looking into a single VMWare server to
> help and possibly begin to replace any server that dies. The new server
> would have at minimum 2 Intel Nehalem 8 core CPUs (or AMD equivalent)
> and 128GB memory. Storage is not an issue since most of the storage
> would be from the NAS device, but the VMs and snapshots would be stored
> locally. The type of work we do in our shop is financial modeling, or
> running simulations on a number of financial instruments, which is very
> memory intensive. Most of the VMs would be running RHEL 5.2 or later
> with possibly a couple of Windows 7 or Windows 2008 server. Our IT
> people are going to purchase and preconfigure the box with the latest
> VMware bare metal product whatever they decide to call it. In any case,
> my concern is with memory use. Some of the things we do, such as the
> modeling is very memory and CPU intensive, and some things much less. I
> don't want to have to configure each VM with a large amount of memory,
> but I would like it to be able to use additional available memory if
> available (eg memory on demand). Some of the VMs would be somewhat
> permanently running, and some would be brought up and down as needed. My
> concern is that 128GB is too limiting, but I'm not sure at this point
> even how the system will be used.
>
> The real question is can we configure a VMWare vSphere ?VM to use
> something like a range from something like 4GB to 64GB. And, if so, can
> the VM that expanded return that back to the pool.

Since no one else responded on list....

I think the closest thing to this is memory overcommit and VMware's
memory ballon driver which takes memory back from VMs without the
guest OS having to be aware of the process.

Here's one web page which discusses it briefly in the context of performance:

http://www.virtualinsanity.com/index.php/2010/02/19/performance-troubleshooting-vmware-vsphere-memory/

I'm sure that you can get lots more info by looking up "ballon driver"
on VMwares web site.

Bill Bogstad